Recently, demand for power MOSFETs has been growing, for instance, in applications for driving vehicle-mounted motors such as in EPS (electrically-assisted power steering). The motor can be driven by e.g. a three-phase inverter and an H-bridge circuit. In a power MOSFET, a recovery current flows because of the presence of energization of the parasitic diode and reverse recovery operation. When this recovery current flows, a prescribed breakdown voltage is required to avoid destruction of the semiconductor by this current (in the following, this tolerance is referred to as trr withstand capability). This also applies to the low-side MOSFET of a synchronous rectification DC-DC converter.
In this context, a trench gate MOSFET having a field plate structure has been drawing attention. In such elements, higher trr withstand capability is required.